1. Field of the Invention
The present invention relates to a vehicle seat drive having a mechanical inchworm linear motion actuator for driving a vehicle seat.
2. Background Art
Vehicle seat drives provide at least six degrees of automated motion. These degrees of motion include fore and aft, up and down, and forward and backward tilting. Typical vehicle seat drives use three separate DC permanent magnet motors that drive ball screws via extensive gearing to accomplish these degrees of motion. Typical vehicle seat drives are heavy and large and take up substantial foot space beneath a vehicle seat. What is needed is a lighter, less complex, and more compact vehicle seat drive which requires fewer components, is relatively cheap to manufacture, and is relatively noiseless during operation. Such a vehicle seat drive would incorporate a mechanical inchworm linear motion actuator.
Existing inchworm linear motion actuators include piezoelectric and magnetostrictive linear actuators. Piezoelectricity is the property by which a material reacts to an applied electric voltage by changing shape and, vice versa, generating an electric current in response to an applied mechanical stress. Piezoelectrics transfer electrical energy into mechanical energy and transfer mechanical energy into electrical energy. Piezoelectrics are often used in precision positioning devices as both actuators and sensors. Piezoelectrics respond only with microscopic dimensional changes, but when multi-layered, macroscopic motions can be produced.
Used in linear and rotary actuators, piezoelectrics allow for simple, highly dynamic designs that can achieve high force density and provide noiseless operation and high holding forces. However, the disadvantages of piezoelectrics include their high cost and undesirable material properties such as hysteresis creep, brittleness, and temperature sensitivity.
In the design of piezoelectric linear actuators, piezoelectric stacks are arranged to produce inchworm motion by alternating clamping and translation. The basic concept behind a piezoelectric inchworm linear motion system 10 is illustrated in FIG. 1A through FIG. 1H. System 10 includes a central piezoelectric actuator 12, left and right clamping piezoelectric actuators 14a and 14b, and a shaft 16. Central actuator 12 performs a length changing function and clamping actuators 14a and 14b perform a clamping function.
In FIG. 1A, system 10 is off and each of actuators 12, 14a, and 14b, are opened and disengaged from shaft 16. In FIG. 1B, left clamping actuator 14a closes and clamps onto shaft 16. This is a representation of the clamping function. In FIG. 1C, central actuator 12 compresses towards shaft 16 and extends thereby moving left clamping actuator 14a with the shaft in the left direction. This is a representation of the length changing function. In FIG. 1D, right clamping actuator 14b closes and clamps onto shaft. In FIG. 1E, left clamping actuator 14a opens and disengages shaft 16. In FIG. 1F, central actuator 12 contracts and shaft 16 moves further in the left direction. In FIG. 1G, left clamping actuator 14a closes and clamps onto shaft 16. In FIG. 1H, the process starts to repeat with right clamping actuator 14b opening and disengaging shaft 16.
System 10 has a very simple design that uses only piezoelectric actuation. Depending upon the electrical input sequence, shaft 16 may be moved in either direction at variable speeds. However, in addition to the other disadvantages noted above, the lack of a self locking state (in the absence of power) is undesirable.
Magnetostriction inchworm linear motion systems use magnetic fields to move special types of metal having magnetostrictive properties. Magnetostriction is the phenomenon in which magnetic energy is transferred into mechanical energy and vice versa. In the first case, known as the Joule effect, magnetostrictive materials change shape in response to a changing magnetic field. The Joule effect is used mainly in actuators where motion or force is the desired outcome. As most devices couple electric and magnetic energy (for example, using electric current with changing magnetic field), magnetostrictive motion systems are really electromagneto-mechanical devices.
The basic physical operation of magnetostriction is as follows. When no magnetic field is applied the domains that make up the molecular structure of magnetostrictive materials are disorganized. Upon exposure to a magnetic field, the domains rotate and align with the magnetic field. The reorientation of the molecular domains causes geometric distortion on the macroscopic level thereby elongating the material along the direction of the magnetic field. As the magnetic field gets stronger, more domains get aligned and greater elongation is achieved.
The main components of a magnetostriction inchworm linear motion system include a magnetostrictive rod and a metal cylindrical housing around which induction coils are wound. The rod inches up and down by stretching and pushing against the sides of the housing. The limiting factor for use of magnetostrictive alloys is cost as these alloys are made from expensive rare earth elements. Accordingly, magnetostriction inchworm linear motion systems are uneconomical to incorporate in the mass assembly of vehicles.
It is an object of the present invention to provide a vehicle seat drive having a mechanical inchworm linear motion actuator for driving a vehicle seat.
It is another object of the present invention to provide a vehicle seat drive having an actuation module and a jamming module for performing length changing and clamping functions to drive a vehicle seat.
It is a further object of the present invention to provide a vehicle seat assembly having a vehicle seat drive including a mechanical inchworm linear motion actuator.
In carrying out the above objects and the other objects, the present invention provides a vehicle seat drive having a linearly movable shaft coupled to the vehicle seat such that the vehicle seat moves as the shaft moves. The vehicle seat drive further includes a jamming module having left and right jamming plates operable for engaging and disengaging the shaft while moving linearly with respect to the shaft. The vehicle seat drive also includes an actuation module operable for applying linear forces on the jamming plates to have the jamming plates engage and disengage the shaft and move linearly with respect to the shaft. The actuation module applies a first linear force in the left direction on the left jamming plate to have the left jamming plate engage and move the shaft in the left direction thereby moving the vehicle seat to the left.
Further, in carrying out the above objects and other objects, the present invention provides a vehicle seat assembly having a vehicle seat and a linearly movable shaft coupled to the vehicle seat such that the vehicle seat moves as the shaft moves. The vehicle seat assembly further includes a jamming module having left and right jamming plates operable for engaging and disengaging the shaft while moving linearly with respect to the shaft. The vehicle seat assembly also includes an actuation module operable for applying linear forces on the jamming plates to have the jamming plates engage and disengage the shaft and move linearly with respect to the shaft. The actuation module applies a first linear force in a first linear direction on one of the jamming plates to have the one of the jamming plates engage and move the shaft in the first linear direction thereby moving the vehicle seat in the first linear direction.
Also, in carrying out the above objects and other objects, the present invention provides a vehicle seat drive for driving a vehicle seat between fore and aft positions. The vehicle seat drive includes an actuation module having a motor, a rotatable shaft, and a wobble plate. The motor is coupled to the rotatable shaft to rotatably drive the rotatable shaft. The wobble plate is coupled to the rotatable shaft to rotate with the rotatable shaft such that a fixed point of the wobble plate has lateral motion as the rotatable shaft rotates. The fixed wobble plate point generates a first linear force during a first rotatable revolution portion and removes the first linear force during a second rotatable revolution portion while rotating. The vehicle seat drive further includes a jamming module having left and right movable jamming plates and a movable shaft. The movable shaft extends through the jamming plates such that the jamming plates are locked to the movable shaft in a biased configuration. The movable shaft is coupled to a vehicle seat such that the vehicle seat moves as the movable shaft moves.
The fixed wobble plate point engages one of the jamming plates as the fixed wobble plate point moves in a first linear direction and provides the first linear force during the first rotatable revolution portion on the one of the jamming plates causing the movable shaft and the jamming plates to move in the first linear direction while causing the other one of the jamming plates to unlock from the movable shaft thereby moving the vehicle seat in the first linear direction. The fixed wobble plate point removes the first linear force during the second rotatable revolution portion from the one of the jamming plates causing the jamming plates to move back to the biased configuration.
Still further, in carrying out the above objects and other objects, the present invention provides a vehicle seat drive for driving a vehicle seat. The vehicle seat drive includes a shaft, a jamming module, and an actuation module. The jamming module includes left and right jamming plates operable for engaging and disengaging the shaft while moving linearly with respect to the shaft. The jamming plates are biased in a biased configuration to engage the shaft and are coupled to the vehicle seat such that the vehicle seat moves as the r jamming plates move. The actuation module includes first and second pairs of push solenoids operable for applying linear forces on the jamming plates to have the jamming plates engage and disengage the shaft and move linearly with respect to the shaft. The first pair of solenoids applies a first linear force in a first linear direction on one of the jamming plates to have the one of the jamming plates move along the shaft in the first linear direction thereby moving the other one of the jamming plates and the vehicle seat in the first linear direction. The second pair of solenoids applies a second linear force in an opposed second linear direction on the other one of the jamming plates to have the other one of the jamming plates move the along the shaft in the second linear direction thereby moving the one jamming plate and the vehicle seat in the second linear direction.
The above objects and other objects, features, and advantages of the present invention are readily apparent from the following detailed description of the detailed description of the preferred embodiment(s) when taken in connection with the accompanying drawings.